Heavy metals in untreated/treated urban effluent and sludge from a biological wastewater treatment plant

The presence of heavy metals in wastewater is one of the main causes of water and soil pollution. The aim of the present study was to investigate the removal of Cd, Cu, Pb, Hg, Mn, Cr and Zn in urban effluent by a biological wastewater treatment, as well as to quantify the levels of As, Be, Cd, Cr,...

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Published in:Environmental science and pollution research international 2007-11, Vol.14 (7), p.483-489, Article 483
Main Authors: Oliveira, Aline da Silva, Bocio, Ana, Trevilato, Tânia M Beltramini, Takayanagui, Angela M Magosso, Domingo, José L, Segura-Muñoz, Susana I
Format: Article
Language:English
Subjects:
Acetylene
Agriculture
Atomic absorption spectrophotometry
Atomizing
Beryllium
Cadmium
Chromium
Copper
Dewatering
Efficiency
Effluents
Heavy metals
Inductively coupled plasma
Iron
Lead
Lead (metal)
Legislation
Manganese
Mass spectrometry
Mass spectroscopy
Mercury
Mercury (metal)
Metal concentrations
Metal industry wastewaters
Metal ions
Metals
Metals, Heavy - analysis
Metals, Heavy - chemistry
Nickel
Sanitation
Sediment pollution
Sewage - chemistry
Sewage sludge
Sludge
Soil contamination
Soil pollution
Soil water
Spectral analysis
Spectrophotometry
Waste water
Wastewater treatment
Wastewater treatment plants
Water - chemistry
Water pollution
Water Purification
Water treatment
Zinc
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Summary:The presence of heavy metals in wastewater is one of the main causes of water and soil pollution. The aim of the present study was to investigate the removal of Cd, Cu, Pb, Hg, Mn, Cr and Zn in urban effluent by a biological wastewater treatment, as well as to quantify the levels of As, Be, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn, Tl, V and Zn in dewatering sludge from the Biological Wastewater Treatment Plant of Ribeirão Preto (RPBWTP), Brazil. Concentrations of Cd, Cr, Cu, Mn and Pb in wastewater and those of Ni in sludge were determined by atomic absorption spectrophotometry with graphite furnace atomization. Mercury concentrations in wastewater were measured by hydride generation atomic spectrophotometry, and Zn levels were determined by atomic absorption spectrophotometry using acetylene flame. In sludge, the levels of As, Be, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Sn, TI, V and Zn were determined by inductively coupled plasma-mass spectrometry. Results. The percentages of removal efficiency (RE) were the following: Hg 61.5%, Cd 60.0%, Zn 44.9%, Cu 44.2%, Pb 39.7%, Cr 16,5% and Mn 10.4%. In turn, the mean concentrations (mg/kg) of metals in dewatering sludge followed this increasing order: Tl (< 0.03), Hg (0.31), Be (0.43), As (1.14), Cd (1.34), V (59.2), Pb (132.1), Sn (166.1), Cr (195.0), Mn (208.1), Ni (239.4), Cu (391.7), Zn (864.4) and Fe (20537). The relationship between metal levels in untreated wastewater, as well as the removal efficiency are in agreement with previous data from various investigators. It is important to note that metal removal efficiency is not only affected by metal ion species and concentration, but also by other conditions such as operating parameters, physical, chemical, and biological factors. Metal values recorded for treated wastewater and sludge were within the maximum permitted levels established by the Environmental Sanitation Company (CETESB), São Paulo, Brazil. There is an urgent need for the authorities who are responsible for legislation on sludge uses in agriculture of establishing safety levels for As, Be, Hg, Sn, Tl and V. According to the current metal levels, RP-BWTP sludge might be used for agriculture purposes. However, for an environmentally safe use of sewage sludge, further studies including systematic monitoring are recommended. Annual metal concentrations and predicted variations of those elements in the sludge should be monitored.
ISSN:0944-1344
1614-7499
DOI:10.1065/espr2006.10.355